The present invention is related to a transmission power control technique capable of suppressing a peak of transmission power required in such a case that using of CDMA (Code Division Multiple Access) type portable telephones by a large number of telephone users is overlapped with each other (namely, during user multiplex-use of portable telephones). More specifically, the present invention is directed to a transmission power control method, a transmission power control apparatus, and a communication apparatus, in which a peak of transmission power does not exceed a limit value.
FIG. 7 is a structural diagram of a transmission peak suppressing device employed in a conventional transmission power control apparatus. This transmission peak suppressing device includes a limit unit 21, and a band-limiting filter unit 22. The limit unit 21 compares transmission data of each channel signal with a limiter threshold value. In the case that the transmission data exceeds the limiter threshold value, this limit unit 21 limits the transmission data to a level which does not exceed the limiter threshold value. In this conventional technique, a time rate defined when the transmission data exceeds the limiter threshold value is detected as a present limiter rate, and the limit unit 21 changes the limiter threshold value so that this present limiter rate is approximated to a defined limiter rate which is previously set. Then, the transmission data which has passed through this limit unit 21 will be filtered by the band-limiting filter unit 22, by which the band-limiting process operation is carried out.
It should be noted that the conventional transmission power control technique is described in, for instance, Japanese Patent Publication No. Hei. 11-136210.
In the above-explained conventional technique, before the transmission data is inputted into the band-limiting filter unit 22, the limit unit 21 limits the amplitude value as to this transmission data in order to suppress the peak factor. As a result, before the transmission data is entered into the band-limiting filter unit 22, the peak factor can be suppressed. However, due to the gain owned by the band-limiting filter unit 22, another peak factor is produced in the transmission signal outputted from the band-limiting filter unit 22. There is such a problem that this peak factor could not be suppressed.